In recent years, various air-conditioning systems have been devised for utilization of solar energy. Some of these systems utilize a closed absorption refrigeration cycle with solar collectors providing the heat input for the concentrator portion of the absorption refrigeration system (see U.S. Pat. Nos. 2,030,350 and 2,221,971). Such systems require high operating temperatures, e.g., about 200.degree. F. for the solar current collector and are thus hampered by low heat collecting efficiency. Other systems utilize an open absorption system for dehumidification of the conditioned air and employ solar heat collectors for the part of the concentrator which receives heat in an indirect heat exchange relationship (see U.S. Pat. Nos. 2,257,485 and 4,011,731). These systems utilize conventional refrigeration or solar-powered closed-absorption of rankine-cycle refrigeration for removing sensible heat of the conditioned air.
Still other systems utilize an open absorption system for dehumidification of the conditioned air in which heat pumps or total energy systems provide both concentrator heat input and refrigeration for sensible heat removal (see U.S. Pat. Nos. 3,247,679; 3,401,530; and 3,488,971). None of these systems utilize solar energy for concentrator heat input.
The above-mentioned systems in some cases accomplish heat storage for storage of collected solar energy for use during nocturnal periods on cloudy days but these storage systems typically store energy on a sensible heat basis, i.e., merely by elevating the temperature of the liquid in the reservoir which is usually water or an anti-freeze solution. Other systems do not include energy storage of any type, and cooling loads must be handled by auxiliary equipment during nocturnal periods or on cloudy days.
Hence, a principal object of the invention is to provide a method and apparatus for conditioning air on a year-round basis thereby providing heating or cooling of the air as the season requires while using solar energy as the primary energy source.
Another object is to provide a solar-powered air-conditioning system having the ability to store cooling capability in the form of concentrated aqueous hygroscopic solution to thereby provide a much greater cooling-energy storage potential per unit volume and per unit cost of the energy storage reservoir than has heretofore been available, and to reduce the amount of auxiliary energy required for operation during nocturnal or extended cloudy periods and periods in which the ambient temperature is lower than room temperatures.
It is also an object to provide a system for conditioning air by utilizing a solar collector through which an aqueous hygroscopic liquid circulates and is piped into heat exchange relationship with the air to be conditioned in both the cooling and the heating modes of operation with a view to improving efficiency in the utilization of solar energy and reducing system complexity and cost.